Boxes and cartons used for the packaging, shipment, and storage of articles of commerce are often constructed to be erectable from and collapsible to flat configurations. These types of boxes are typically constructed from cardboard blanks that have score lines along which the sides of the boxes may be folded about their bottoms. Some of them have their sides bonded in place with sealing agents and adhesives. These types however take prolonged time to construct due to the time required for the adhesive to set. Also, once that type of box or carton is constructed it can not be disassembled and returned to a flat blank configuration for storage and reuse.
Cartons and boxes made from cardboard blanks have also long been devised which have their sides held uprightly by means of interfitting tabs and slots which avoid the need for adhesives. These corner-lock type boxes typically are configured from cardboard blanks that have side corner retention means in the form of extended portions or tongues that may be extended through slits. Exemplary of such is the one shown in U.S. Pat. No. 4,216,897. These types of corner locks however can have substantial forces exerted upon them thus causing material stress and deformation. With prolonged use and repeated assemblies and disassemblies, the tongues and slits can deform, enlarge and rip. Another problem associated with these type boxes is their limited ability to support other loaded boxes stacked one upon another without crinkling their walls.
It thus is seen that a collapsible box erectable from a blank with corner-locking means and with the ability of supporting other boxes without substantially weakening has long remained an elusive goal. Accordingly, it is to the provision of such a box that the present invention is primarily directed.